Variable transformer with rotating coil



B. ZLACHEVSKY VARIABLE TRANSFORMER WITH ROTATING COIL March 29, 1966 2 Sheets-Sheet 1 Filed May 29, 1963 AC OUTPUT AC INPUT AC OUTPUT FIG.

FIG.

INVENTOR.

BANET ZLACHEVSKY BY ATTORNEY March 29, 1966 B. ZLACHEVSKY VARIABLE TRANSFORMER WITH ROTATING COIL Filed May 29, 1963 2 Sheets-Sheet 2 FIG.

INVENTOR.

BANET ZLACHEVSKY Y Wwm ATTORNEY United States Patent York Filed May 29, 1963, Ser. No. 284,102 6 Claims. (Cl. 336-141);

The present invention. concerns: variable alternatingcurrent transformers and, in particular, such transformers utilizing a rotating coil structure.

Variable transformers for alternating current voltage control are widely used. One of the most popular forms utilizes a toroidal core and single layer winding with a rotatable brush to pick off the desired voltage. This type of variable transformer has been widely distributed under the trade mark Variac. Since the voltage pick olf brush at times contacts two turns of the coil, some means must be employed to keep the current in the shorted turn which this creates within limits. The limiting of the shorted turn current is most commonly accomplished by the use of a pick off brush hav ing substantial current limiting resistance. In this connection provision must also be made to dissipate the heat due to load and shorted turn current flowing in the resistance brush. While the above described construction may work fairly well at low or moderate currents, the at tendant problems become very formidable at high currents.

Attempts have been made to solve some of the problems outlined above by utilizing a solenoid type of winding with a brush which is rotated so that it tracks along a single turn. This apparent simple solution to the problem is found to create another problem and that is the one of conducting current into the coil at a fixed point. A commutator at one or both ends of the coil, for example, acts as a shorted turn which cannot be tolerated especially in transformers supplying high currents at low voltages.

According to the present invention, a single layer solenoid type coil embracing a magnetic core structure is rotated and is provided with one or two stationary brush contacts and one or more movable brush contacts riding on a single turn. Since the movable contact touches only a single turn, no turns are shorted and a low resistance brush may be used.

According to the present invention, the problem of the stationary or end contact or contacts is solved by a unique combination of a spit commutator and a reverse wound end turn. One half of the split commutator is connected to a point one turn before the start of the reverse wound end turn and the other half is connected to the end of the reverse wound end turn. These two points are always at the same potential and hence no shorted turn current will flow when the pick off brush contacts the two halves of the split commutator.

Accordingly, one object of the present invention is to provide a variable output alternating current transformer free from shorted turn problems.

Still another object is to provide a variable output alternating current transformer capable of operating at extremely high currents.

A further object it to provide a variable output alternating current transformer exhibiting higher efiiciency, longer life and less trouble than those hitherto available.

These and other objects will be apparent from the detailed description of the invention given in connection with the various figures of the drawing.

In the drawing:

FIGURE 1 is a schematic representation of one form of the present invention.

FIGURE 2 is a schematic rcpresentation'of a modifiedform of the present invention.

FIGURE 3 is. a general view of the construction of one form of the present invention.

FIG. 1 shows a magnetic core 1 carrying a solenoid coil winding 2 having a single reverse wound turn 3 at one end and a second single reverse wound turn; 4 at the other end. A split communtator 5-6 is provided concentric with winding 2. The half commutator segment 5 is connected over lead- 7 to the end of reverse wound turn 3 at its end point 20 and half commutator segment 6 is connected over lead 8 to point 17 which is accurately placed at one full turn on coil 2 before the start of reverse wound turn 3. Similarly at the other end of coil 2 a second split commutator 13-14 is provided. The half commutator segment 13 is connected over lead 15 to the end of reverse wound turn 4 at its end point 19 and half commutator segment 14 is connected over lead 16 to point 18 on coil 2 which is located accurately at one full turn on coil 2 before the start of reverse Wound turn 4. The connections over leads 7 and 8 to segments 5 and 6 respectively are conveniently made at or near the adjacent ends of these segments. Similarly the connections over leads 15 and 16 to segments 13 and 14 respectively are conveniently made at or near the adjacent ends of these segments.

The input to the variable transformer is made over leads 9 and 24 to stationary brushes 10 and 21 respectively. The output is taken from movable contact 12 which tracks along the turns of coil 2 as it is rotated along with the commutator segments in contact with the stationary brushes. The output is taken from movable contact 12 over lead 11 and one end of the input circuit as point 23 over lead 22. Thus, as coil 2 is rotated, movable contact 12 tracking along coil 2 picks off a variable portion of the input voltage.

FIG. 2 shows a modified circuit in which the input over leads 25 and 27 is applied to a stationary primary 26 wound on core 1 and secondary 2 adapted to embrace both core and primary windings is rotated to provide a variable output as described in connection with FIG. 1. In this case only one stationary contact 21 and the variable contact 12 are required and the output is taken over leads 11 and 22.

FIG. 3 is a general view of how the device according to the present invention may be constructed. Correspending numbers designate parts designated by the same numbers in FIGS. 1 and 2. While any suitable means may be employed to rotate coil 2, a simple hand knob 30 on shaft 29 is shown to rotate worm 28 meshing with worm gear 31 mechanically attached to coil 2. The moving brush may be made movable by mounting it on a slider 34 freely movable along a rail 33. Since the coil of the present invention may also be used as a variable inductor, a gap in core 1 as at 32 may be provide-d to increase the Q of the circuit.

While only a few forms of the present invention have been shown and described, many modifications will be apparent to those skilled in the art and within the spirit and scope of the invention as set forth in particular in the appended claims.

What is claimed is:

1. In a variable output alternating current'transformer, the combination of, a magnetic core, a solenoid coil embracing at least a portion of said core, means for rotating said coil about its axis, a two part split commutator mounted on one end of said coil and rotatable therewith, a reverse wound single turn at the commutator end of said coil, a connection between said reverse wound turn and one part of said commutator, a connection between a point on said coil at a potential point substantially equal to the potential at the first said connection and the second of said commutator parts a stationary brush in contact with one of said commutator parts, and a movable brush in contact with said coil.

2. A variable output alternating current transformer as set forth in claim 1 and including a second two part split commutator, a second reverse wound turn and a second stationary brush.

3. A variable output alternating current transformer as set forth in claim 1 and including a second coil wound within said solenoid coil. 7

4. A'variable output alternating current transformer as set forth in claim 1 wherein said core is a threelegged-core and the solenoid coil is wound around the center leg.

5. A variable inductor including, in combination, a

magnetic core, a rotatable solenoid coil embracing at least a portion of said core, two commutator segments connected to equipotential points on said coil, a stationary brush in contact with at least one of said segments, and a movable brush in contact with said coil.

6. A variable inductor as set forth in claim 5 wherein one of said equipotential points is formed by means of a reverse wound turn at one end of said solenoid. 

5. A VARIABLE INDUCTOR INCLUDING, IN COMBINATION, A MAGNETIC CORE, A ROTATABLE SOLENOID COIL EMBRACING AT LEST A PORTION OF SAID CORE, TWO COMMUTATOR SEGMENTS CONNECTED TO EQUIPOTENTIAL POINTS ON SAID COIL, A STATIONARY BRUSH IN CONTACT WITH AT LEAST ONE OF SAID SEGMENTS, AND A MOVABLE BRUSH IN CONTACT WITH SAID COIL. 